Configure the source to send the configured source interface IP address instead of using its front-end IP address in the ICMPunreachable messages and in the traceroute command output. Use the ip icmp source-interface interface or theipv6 icmp source-interface interface commands in Configuration mode to enable the ICMP error messages to besent with the source interface IP address. This functionality is supported on loopback, VLAN, port channel, and physical interfacesfor IPv4 and IPv6 messages. feature is not supported on tunnel interfaces. ICMP error relay, PATH MTU transmission, andfragmented packets are not supported for tunnel interfaces. The traceroute utilities for IPv4 and IPv6 list the IP addresses of thedevices in the hops of the path for which ICMP source interface is configured.Configuring the Duration to Establish a TCP ConnectionYou can configure the duration for which the device must wait before it attempts to establish a TCP connection. Using thiscapability, you can limit the wait times for TCP connection requests. Upon responding to the initial SYN packet that requests aconnection to the router for a specific service (such as SSH or BGP) with a SYN ACK, the router waits for a period of time for theACK packet to be sent from the requesting host that will establish the TCP connection.You can set this duration or interval for which the TCP connection waits to be established to a significantly high value to prevent thedevice from moving into an out-of-service condition or becoming unresponsive during a SYN flood attack that occurs on the device.You can set the wait time to be 10 seconds or lower. If the device does not contain any BGP connections with the BGP neighborsacross WAN links, you must set this interval to a higher value, depending on the complexity of your network and the configurationattributes.To configure the duration for which the device waits for the ACK packet to be sent from the requesting host to establish the TCPconnection, perform the following steps:1. Define the wait duration in seconds for the TCP connection to be established.CONFIGURATION modeDell(conf)#ip tcp reduced-syn-ack-wait <9-75>You can use the no ip tcp reduced-syn-ack-wait command to restore the default behavior, which causes the waitperiod to be set as 8 seconds.2. View the interval that you configured for the device to wait before the TCP connection is attempted to be established.EXEC modeDell>show ip tcp reduced-syn-ack-waitEnabling Directed BroadcastBy default, Dell Networking OS drops directed broadcast packets destined for an interface. This default setting provides someprotection against denial of service (DoS) attacks.To enable Dell Networking OS to receive directed broadcasts, use the following command.• Enable directed broadcast.INTERFACE modeip directed-broadcastTo view the configuration, use the show config command in INTERFACE mode.Resolution of Host NamesDomain name service (DNS) maps host names to IP addresses. This feature simplifies commands such as Telnet and FTP by allowingyou to enter a name instead of an IP address.Dynamic resolution of host names is disabled by default. Unless you enable the feature, the system resolves only host names enteredinto the host table with the ip host command.IPv4 Routing 407
